This invention relates to hydroxyl-terminated polybutadiene compositions, curable compositions comprising such hydroxyl-terminated polybutadienes, resin products made by reacting such hydroxyl-terminated polybutadienes with polyisocyantes, epoxy resins, anhydrides, amines, or phenolics, and cured polymers based on such formulations such as polyurethanes.
Prior hydroxyl-terminated polybutadienes prepared by radical polymerization, such as commercially available ones sold under the designations Poly bd R45HTLO or Liquiflex P, contain a large percentage of oligomers and polymers with branched microstructures and more than 2.0 hydroxyl functionalities per molecule, with an average functionality of such polybutadienes is about 2.4-2.6 hydroxyl groups per polymer molecule. Polyurethane formulations prepared from such branched hydroxyl-terminated polybutadienes reacted with polyisocyanates exhibit low tensile and tear strength properties.
Prior hydroxyl-terminated polybutadienes derived from anionic polymerization, such as Krasol(copyright) LBH 2000, 3000 and 5000, and the Nisso-G series have a non-branched structure and a maximum of 2.0 hydroxyl functionalities per chain, typically 1.8-1.9 hydroxyl groups per polymer chain. Such non-branched hydroxyl-terminated polybutadienes have been used in the prior art for reaction with organic polyisocyanates, to form polyurethanes or urethane-terminated prepolymers.
It has been a longstanding objective of those skilled in this art to form polyurethanes with improved and unique combination of properties, and to form prepolymers with lower viscosity and with improved storage stability thereof.
It has also been an objective in this art to improve the thermoplasticity and modulus of the chain extended cured resins of this type.
These objects, and others which will become apparent from the following disclosure, are achieved by the present invention which in one aspect comprises a composition comprising (A) non-branched hydroxyl-terminated polybutadiene having hydroxyl functionality lower than 2 per molecule by average; and (B) hydroxyl-terminated polybutadiene having hydroxyl functionality greater than 2 per molecule by average, the weight ratio of (A) to (B) being about 99:1 to 1:99. Preferably the weight ratio is 90:10 to 10:90.
In another aspect the invention comprises mixtures of (A) and (B) with an organic polyisocyanate to form polyurethane resins, isocyanate-terminated prepolymers prepared from such mixture or chain extended thermoplastic resins prepared by reacting the isocyanate terminated prepolymers with a chain extender such as a diol.
In another aspect, the invention comprises reaction products of the mixtures of (A) and (B) with anhydrides to form carboxyl-terminated prepolymers, with peracids to form epoxy-functionalized resins, with epoxy resins to form epoxy-terminated prepolymers, with phenolics to form phenol-terminated prepolymers, or with amines to form amine-terminated polymers, all or which are curable by reacting with chain extenders or curing agents.
Another aspect of the invention is direct cured polyurethane resins prepared by reacting an organic polyisocyanate with a mixture of (A) and (B).
In still another aspect, the invention comprises a method of preparing hydroxyl-terminated polybutadienes by blending types (A) and (B) in a ratio of 99:1 to 1:99 by weight, and of preparing prepolymers therefrom and of preparing cured resins from the prepolymers.
Suitable non-branched hydroxyl-terminated polybutadienes (A) are low molecular weight resins, preferably having a weight average molecular weight, Mw, of about 1000 to 20,000, more preferably about 2000 to 10,000, and a 1,2-vinyl content of about 15-90 mole percent, preferably 20 to 70 mole %, with an average hydroxyl functionality less than or equal to 2 per molecule. These non-branched polybutadienes are preferably derived from anionic polymerization. The hydroxyl groups can be primary or secondary. Krasol(copyright) LBH 2000, 3000 and 5000, and the Nisso-G series are examples of such non-branched hydroxyl-terminated polybutadienes.
Suitable branched hydroxyl-terminated polybutadienes (B) are also low molecular weight resins, with a preferred number average molecular weight, Mn, of about 1000 to 20,000, more preferably about 2000 to 10,000, and have a 1,2-vinyl content of about 15-90 mole percent, preferably 20 to 70 mole % and an average hydroxyl functionality of more than 2.0, preferably about 2.4-2.6 per molecule. These branched polybutadienes are preferably derived from radical polymerization. The hydroxyl groups can be primary, secondary, or tertiary. Poly bd R45HTLO, Poly bd R45M, Poly bd R20LM, Liquiflex(copyright) H, and Liquiflex(copyright) P are examples of such branched hydroxyl-terminated polybutadienes.
The hydroxyl-terminated polybutadiene mixture compositions can further comprise hydrogenated branched or non-branched hydroxyl-terminated polybutadiene which results in improved high temperature stability with lower concentration of unsaturation. Hydrogenated hydroxyl-terminated polyisoprene, such as Epol(copyright) resin, can also be used as the branched hydroxyl-terminated polybutadiene.
The hydroxyl-terminated polybutadiene mixtures of (A) and (B) and any additional polybutadienes can be mixed with polyisocyanate and reacted to form isocyanate-terminated polyurethane prepolymers which can be further reacted with chain extenders to form resins which have good tensile and tear strength but with, surprisingly, similar modulus when compared with polyisocyanates prepared from (B) alone, as is typical in the prior art.
Suitable polyisocyanates are those with two or more isocyanate groups per molecule on average, for example 4,4xe2x80x2-methylenebis(phenyl isocyanate) (MDI), toluene diisocyanate (TDI), hexane diisocyanate, and others as are well known in this art.
The cured polyurethane of the invention exhibit greatly improved tensile and tear strength properties compared to the polyurethanes made from radical produced hydroxyl-terminated polybutadienes having terminal hydroxyl functionality of 2.4 to 2.6, but have high moduli compared to polyurethanes made from the anionic-produced hydroxyl-terminated polybutadienes.
The cured polymers are characterized by exceptional flexibility and toughness and high modulus properties. Moreover, they possess excellent water resistance and superior low dielectric properties. This combination of properties is not achievable with compositions of the prior art.
While the urethane polymers and isocyanate-terminated prepolymers cured with diols are preferred uses of the types of resins of the invention, the hydroxyl-terminated polybutadienes can also be reacted to form carboxyl, phenol, epoxy or amine-terminated polybutadienes, which can be cured to produce resins which also exhibit the improved properties. The cured thermoplastic resins are useful in a wide variety of applications such as coatings, adhesives, membranes, brake fluids, for example.